Polymers of polyhydroxyalkanoate or polyhydroxyalkanoic acid (PHA) type, such as polylactic acid (PLA), are polymers that may be obtained from a monomer of plant origin. They are of major interest on account of their biodegradable properties. However, they are particularly fragile polymers, which require reinforcing with respect to impact.
JP H-09-316310 describes PLA compositions containing ethylene-glycidyl methacrylate copolymers grafted with polystyrene or polydimethacrylate, or alternatively polyolefins grafted with maleic anhydride.
WO 2005/059031 describes a PLA composition comprising from 3% to 40% by mass of a copolymer of ethylene, of a carboxylic acid ester and of a glycidyl ester.
US 2008/0071008 discloses a polyhydroalkanoic acid composition comprising from 0.2% to 10% of core-shell compound with a refractive index of less than 1.5 and not comprising any vinyl aromatic monomer.
While these compositions show improved impact strength, this strength is not entirely satisfactory.
Moreover, some of these compositions have a fluidity that is markedly inferior to that of PHA. This substantial reduction in fluidity hampers the use, most particularly for thin and large-sized injection-molded parts.
The aim of the present invention is to propose a novel PHA composition that has good impact strength especially at low total loading levels of impact modifier.